commit fb49a4123a2cb1e18d3b62a8d9c8789ba8f008c7
author Andrew Walbran <qwandor@google.com> Wed Jan 15 12:14:24 2025 +0000
committer Andrew Walbran <qwandor@google.com> Wed Jan 15 16:18:54 2025 +0000
tree f6091ddbe5e69f4af49fe2f5f14b9730d0c87436
parent 72e4e12aaaf20b3ffa28d227af8ce96ddeb6e619

Avoid using static mut variables.

Test: m vmbase_example_kernel_bin
Change-Id: I366cc93f63a5a759aa94f09b32368c0a0b05708e

guest/vmbase_example/Android.bp

diff --git a/guest/vmbase_example/Android.bp b/guest/vmbase_example/Android.bp
index ab21191..e5dfc2a 100644
--- a/guest/vmbase_example/Android.bp
+++ b/guest/vmbase_example/Android.bp
@@ -12,6 +12,7 @@
         "libdiced_open_dice_nostd",
         "liblibfdt_nostd",
         "liblog_rust_nostd",
+        "libspin_nostd",
         "libvirtio_drivers",
         "libvmbase",
     ],

guest/vmbase_example/src/main.rs

diff --git a/guest/vmbase_example/src/main.rs b/guest/vmbase_example/src/main.rs
index 52a5f3e..b7d2f95 100644
--- a/guest/vmbase_example/src/main.rs
+++ b/guest/vmbase_example/src/main.rs
@@ -28,6 +28,7 @@
 use alloc::{vec, vec::Vec};
 use libfdt::Fdt;
 use log::{debug, error, info, trace, warn, LevelFilter};
+use spin::mutex::SpinMutex;
 use vmbase::{
     bionic, configure_heap,
     fdt::pci::PciInfo,
@@ -38,8 +39,8 @@
 };
 
 static INITIALISED_DATA: [u32; 4] = [1, 2, 3, 4];
-static mut ZEROED_DATA: [u32; 10] = [0; 10];
-static mut MUTABLE_DATA: [u32; 4] = [1, 2, 3, 4];
+static ZEROED_DATA: SpinMutex<[u32; 10]> = SpinMutex::new([0; 10]);
+static MUTABLE_DATA: SpinMutex<[u32; 4]> = SpinMutex::new([1, 2, 3, 4]);
 
 generate_image_header!();
 main!(main);
@@ -100,25 +101,18 @@
     );
 }
 
-#[allow(static_mut_refs)]
 fn check_data() {
     info!("INITIALISED_DATA: {:?}", INITIALISED_DATA.as_ptr());
-    // SAFETY: We only print the addresses of the static mutable variable, not actually access it.
-    info!("ZEROED_DATA: {:?}", unsafe { ZEROED_DATA.as_ptr() });
-    // SAFETY: We only print the addresses of the static mutable variable, not actually access it.
-    info!("MUTABLE_DATA: {:?}", unsafe { MUTABLE_DATA.as_ptr() });
 
     assert_eq!(INITIALISED_DATA[0], 1);
     assert_eq!(INITIALISED_DATA[1], 2);
     assert_eq!(INITIALISED_DATA[2], 3);
     assert_eq!(INITIALISED_DATA[3], 4);
 
-    // SAFETY: Nowhere else in the program accesses this static mutable variable, so there is no
-    // chance of concurrent access.
-    let zeroed_data = unsafe { &mut ZEROED_DATA };
-    // SAFETY: Nowhere else in the program accesses this static mutable variable, so there is no
-    // chance of concurrent access.
-    let mutable_data = unsafe { &mut MUTABLE_DATA };
+    let zeroed_data = &mut *ZEROED_DATA.lock();
+    let mutable_data = &mut *MUTABLE_DATA.lock();
+    info!("ZEROED_DATA: {:?}", zeroed_data.as_ptr());
+    info!("MUTABLE_DATA: {:?}", mutable_data.as_ptr());
 
     for element in zeroed_data.iter() {
         assert_eq!(*element, 0);